5,711 research outputs found

    Towards measurement and verification of energy performance under the framework of the European directive for energy performance of buildings

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    Directive 2002/91/EC of the European Parliament and Council on the Energy Performance of Buildings has led to major developments in energy policies followed by the EU Member States. The national energy performance targets for the built environment are mostly rooted in the Building Regulations that are shaped by this Directive. Article 3 of this Directive requires a methodology to calculate energy performance of buildings under standardised operating conditions. Overwhelming evidence suggests that actual energy performance is often significantly higher than this standardised and theoretical performance. The risk is national energy saving targets may not be achieved in practice. The UK evidence for the education and office sectors is presented in this paper. A measurement and verification plan is proposed to compare actual energy performance of a building with its theoretical performance using calibrated thermal modelling. Consequently, the intended vs. actual energy performance can be established under identical operating conditions. This can help identify the shortcomings of construction process and building procurement. Once energy performance gap is determined with reasonable accuracy and root causes identified, effective measures could be adopted to remedy or offset this gap

    Impact of an occupancy and activity based window use model on the prediction of the residential energy use and thermal comfort

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    The opening of windows can lead to high energy losses in wintertime, especially in nearly zero-energy buildings. But can reduce overheating significantly in summertime. Therefore, window use models have been created in the past to assess the energy use and thermal comfort in residential buildings. The models are mostly based on weather-variables. However, a recent study (Verbruggen, Janssens, et al. 2018) indicated that these models were not able to accurately predict the window use in wintertime. For that reason, an occupancy and activity based model was developed. In this article, the impact of the application of the new window opening model on the residential energy use and thermal comfort was assessed. The object-oriented modelling language Modelica was used to simulate the energy use and temperatures in a nearly-zero energy house, which is a representation of an existing house in a nearly zero-energy neighbourhood in Kortrijk. From this neighbourhood, measured energy use data was available as well as window sensor data for some of the houses. These measured data were compared to the simulated data of the new window use model, a weather-based model and the Belgian EPBD-calculation method. The occupancy and activity based model could predict more accurately the average opening durations in wintertime and could better account for the large variation in window use compared to weather-based models. An optimal window opening strategy could limit the overheating significantly, even prevent it in the bedrooms and bathroom. However, opening the windows also implies an increase in energy use for heating. Some combinations of different window opening habits can limit the overheating, while limiting the increase in energy use at the same time

    EPBD cost-optimal analysis for non-residential buildings in Malta

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    The Energy Performance of Buildings Directive (EPBD) 2010/31/EU requires EU Member States to calculate the cost-optimal levels of minimum energy performance requirements for new buildings and buildings that undergo major renovation. The European Commission Delegated Regulation (EU) No 244/2012 and accompanying Guidelines 2012/C 115/01 establish a comparative methodology with regards to number of reference buildings for each building category, number of energy efficiency measures to be implemented in the study and the minimum level of cost analysis that is required. This paper fulfils the above requirements but also introduces an innovative approach that goes beyond the minimum requirements for the cost-optimal study, whereby a two-stage optimisation approach was undertaken. The first stage focuses on choosing a representative set of combined building envelope measures that cover the full range of possible energy performance levels, in such a way that these lie along the line of minimum space conditioning costs, known as the Pareto Front. While the second stage applies combinations of energy systems’ upgrades to the selected iterations of stage 1. The scope is to minimize the time cost of these cost-optimal studies without sacrificing on their effectiveness or creating biased results. Cost optimal and nearly-zero energy levels were found for homes for the elderly, hotels, offices, restaurants, shops and sports complexes. Results showed that cost optimal levels are best achieved through upgrades of energy systems and solar shading rather than building envelope U-value upgrades for all building categories. This is primarily a result of the mild Mediterranean climate of Malta. Solar water heating and solar photovoltaics have shown to be cost optimal for all categories, except where these cannot be installed such as in shops and restaurants. Shading, heat pump water heaters and high efficiency air-conditioning systems have also been identified as cost-optimal measures.peer-reviewe

    Statistical study on the link between real energy use, official energy performance and inhabitants of low energy houses

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    Energy performance regulations are becoming increasingly strict and governments supply simplified calculation tools to assess whether new buildings fulfil the requirements. However, one can wonder what the accuracy of those tools is for assessing the next generation of houses, that will have to fulfil the upcoming energy requirements. In order to investigate the discrepancy between predicted and real energy use in low energy houses, 537 dwellings were analysed. Data on building characteristics and theoretical energy use from the Flemish EPBD-database was complemented with data from the energy utilities and a survey of the inhabiting households, providing information about the households, their user behaviour and real energy use. While an undeniable correlation was found between theoretical and real energy use, the EPBD-method overestimated the heating energy use for most of the cases. Two building related parameters and two user related parameters proved to have a significant impact on that gap: the use of default values for the air tightness of the envelop and for the efficiency of the gas boiler, the heating profiles of the master bedrooms and the amount of baths and showers taken by the inhabitants. However, two comments must be made. First, the dataset consists of early adopters who could afford such energy performance years before it would be imposed and are therefore not representative of the average household. In addition, the analysis showed significant correlations between household characteristics on the one hand and building characteristics and performance on the other. These last two points question the possibility to extrapolate findings from samples of existing forerunners towards prognoses on future, entire building stock level

    Airtightness assessment of single family houses in Belgium

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    Airtight construction lies at the heart of achieving high energy performance in dwellings. But how well does it apply in new construction? This paper presents results from airtightness measurements on 44 randomly selected, standard new built single family houses in Belgium and from 4 case studies including 78 additional measurements. The houses were randomly selected after completion, to assure that standard workmanship was used during construction. Where applicable, the effect of incorporating the attic and garage in the building volume was measured by performing a series of tests in different configurations. The results are compared with those from a previous study in the early 1990's, with a database that was compiled with results from 161 air tightness reports executed on newly built dwellings by private party consultants and with the governmental EPBD-database (1884 measurements). The results show that the mean leakage rate is about 6 ACH(50) for the randomly selected houses and 3 ACH(50) for the houses in the databases. The houses in the databases are measured upon the initiative of the owner. Therefore, the attention to airtight workmanship is substantially higher for these cases than in the randomly selected houses. This clearly demonstrates the difference between 'mainstream' workmanship and results obtained by the 'engaged' market

    Energy efficiency of social housing existing buildings – a portuguese case study

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    The European energy performance building regulations, Directive 2002/91/EC - Energy Performance of Buildings Directive (EPBD) of the European Parliament and Council, require that new buildings present minimum standards of energy efficiency. Accordingly the Portuguese regulations require that new buildings comply with minimum requirements on the energy performance and must have an energy performance certification through witch an energy efficiency label is attributed to the housing. It also require that existing buildings must have an efficiency energy label when submitted to a commercial transaction or to a deep rehabilitation. To achieve this goal the study of energy performance of existing buildings must be done. As many essentials elements to determine the U-factor and other thermal parameters are unknown, Portugal developed a simplified methodology to achieve the thermal performance of existing buildings. The aim of this paper is to present the study of the energy performance of a set of social dwellings that were constructed during the decade of 80, constructed before the former building thermal comfort specifications came into force. During the study the referred methodology was applied and conclusions of the energy efficiency label obtained were put out as the encountered difficulties. The study also compares the results obtained by the simplified methodology and by the detailed methodology that is required by Portuguese building thermal comfort specifications

    The influence of user behaviour on energy use in old dwellings: case-study analysis of a social housing neighbourhood

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    Taking user behaviour into account to predict the real energy use and possible savings in houses, remains a challenge of huge importance for the Belgian social housing sector, which owns large buildings stocks in urgent need of refurbishment. Within this context, a case-study analysis was carried out on 36 (nearly) identical social houses from a single neighbourhood, dating from the sixties. Information on user behaviour, indoor air quality and thermal comfort was gathered both through in-situ measurements and through surveys of the inhabitants. Furthermore, air tightness and heat flux measurements aimed at increasing the accurate knowledge of the buildings’ characteristics and data on real energy use were gathered. This paper presents some findings from this case study, focusing on the energy use for heating. The huge differences in energy use observed between households on the one hand and between theoretic EPBD-calculations and real measurements on the other hand are investigated. The findings from the measurements and the surveys are implemented in an improved multi-zone quasi-steady state calculation code reaching much better correlations with the real energy figures. This illustrates the influence of some behavioural parameters and the usefulness of both sources of information: surveys and measurements. Remaining causes of discrepancies are further reported

    Sensitivity analyses of thermal bridges: confrontation with the new Belgian EPB-methodology

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    As governments continue to impose more and higher energetic requirements for buildings, they also need better assessment-tools to take into account as many parameters as possible. This results in continuous developments of new calculation methods and softwares, where a balance has to be found between practicality and accuracy. To answer this problem, specifically with regard to the thermal bridges, the three Belgian regions developed a new and common pragmatic approach for assessing thermal bridges, confronting them either to simple basic rules of thumb or to maximal heat transmission coefficients, depending on the type of junction. While thermal bridges that don’t meet the requirements are sanctioned, thermal bridges that perform better can be taken into account to lower the calculated heat-losses. For this project, several very common thermal bridges were selected. Sensitivity analyse are carried out for the different parameters, such as dimensions and thermal conductivity of the components. The calculated heat transfer coefficients are confronted with the boundary-(‘limit-’)values and the default-values of the new methodology. Nevertheless, these analyses weren’t meant as a test for the methodology. They aim at allowing designers to quickly assess their common building details to the new regulation, without having to do preliminary numerical simulations of each individual thermal bridge. They also help them to better understand the correlations between the parameters of the building detail and the resulting heat transmission coefficients. The challenge that rose, was to summarize the results in pragmatic, straight-forward formats
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